Nonblocking networked control of discrete event systems

Networked control is now widely used in engineering systems. We have studied networked supervisory control of discrete event systems in several previous papers. In this paper, we investigate the issue of blocking in networked supervisory control. Due to randomness in communication delays, the issue of blocking is much more complex in networked systems. More conditions need to be satisfied in order to ensure that a supervised system is nonblocking. In this paper, we derive a necessary and sufficient condition for the existence of a nonblocking networked supervisor. The condition is stated in terms of L
_m
(G)-closure, delay controllability and delay observability. Examples are used to illustrate the results.